Pointing out that no fixed standard was recognized for testing the propriety of the interference on the part of the community with its individual members, he finds the test in self-protection, that is, the prevention of harm to others. He bases the proposition not on abstract rights, but on "utility, in the largest sense, grounded on the permanent interests of man as a progressive being." He then uses the following argument to show that to silence opinion and discussion is always contrary to those permanent interests. Those who would suppress an opinion (it is assumed that they are honest) deny its truth, but they are not infallible. They may be wrong, or right, or partly wrong and partly right. (1) If they are wrong and the opinion they would crush is true, they have robbed, or done their utmost to rob, mankind of a truth. They will say: But we were justified, for we exercised our judgment to the best of our ability, and are we to be told that because our judgment is fallible we are not to use it? We forbade the propagation of an opinion which we were sure was false and pernicious; this implies no greater claim to infallibility than any act done by public authority. If we are to act at all, we must assume our own opinion to be true. To this Mill acutely replies: "There is the greatest differ-
